(1) Field of the Invention:
The present invention relates to a novel polynuclear polyhydric phenol, a polyepoxy compound derived therefrom and a process for the preparation thereof. Furthermore, the present invention provides a curable epoxy resin composition having excellent heat resistance characteristics such as high glass transition point, high heat distortion temperature and high heat-resistant elastic property.
(2) Description of the Prior Art:
Various polyepoxy compounds have heretofore been proposed as components to be incorporated into curable epoxy resin compositions. In the fields of molding materials, varnishes, laminates for printed circuits, advanced composite materials and the like, curable epoxy resin compositions excellent in heat resistance characteristics such as glass transition point, heat distortion temperature and heat-resistant elastic property have recently been eagerly required. As the polyepoxy compound constituting a heat-resistant curable epoxy resin composition, there have been used epoxidized phenol-novolak resins, epoxidized o-cresol-novolak resins, polyglycidyl ethers of polynuclear polyhydric phenols such as 1,1,2,2-tetrakis(p-hydroxyphenyl)ethane tetraglycidyl ether, and polyglycidyl compounds of aromatic polyamines such as a tetraglycidyl compound of xylylene diamine, a hexaglycidyl compound of 1,3,5-triaminomethylbenzil and a triglycidyl compound of isocyanuric acid. However, curable epoxy resin compositions including these polyepoxy compounds are still insufficient in the above-mentioned heat resistance characteristics, and they cannot be used in the fields where high heat resistance characteristics are required. Therefore, development of curable epoxy resin compositions having improved heat resistance characteristics has been desired.
Many polynuclear polyhydric phenols are known in addition to the above-mentioned polynuclear polyhydric phenols. For example, there have been proposed polynuclear polyhydric phenols such as .omega.,.omega.'-bis(3,4-dihydroxyphenyl)xylene (Japanese Patent Publication No. 13869/62) 2,4-bis(2,4-dimethylbenzyl)-6-(2-hydroxybenzyl)phenol [Hiroshi Kakiuchi and Yoshio Tanaka; Polymer Chemistry, 20, 643 (1963)], 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane and 1,1,5,5-tetrakis(4-hydroxyphenyl)pentane [D, Aelony; J. Applied Polymer Sci., 4, 141 (1960)], 1,3-bis(2-p-hydroxyphenyl-2-propyl)benzene (Japanese Patent Application Laid-Open Specification No. 13528/83), and 1,4-bis(2-p-hydroxyphenyl-2-propyl)benzene (Japanese Patent Application Laid-Open Specification No. 18331/83). However, even if polyglycidyl ethers of these compounds are used for curable epoxy resin compositions, the above-mentioned heat resistance characteristics are still insufficient, and the compositions cannot be used in the fields where high heat resistance characteristics are required.